Electrophotographic photoreceptor and image-forming apparatus

ABSTRACT

It is to provide a sheet-shaped electrophotographic photoreceptor which has an uncoated area, is good in mechanical adhesiveness between the photosensitive layer and the sheet-shaped conductive substrate but excellent ease of peeling with a solvent, and is further good in electrical properties. The electrophotographic photoreceptor comprises a sheet-shaped conductive substrate and a photosensitive layer provided thereon, wherein the electrophotographic photoreceptor contains a photosensitive layer-uncoated area within the sheet surface, and the photosensitive layer contains a copolycarbonate resin having an extremely restricted specific structure.

TECHNICAL FIELD

The present invention relates to a sheet-shaped electrophotographicphotoreceptor for use in on-demand printers, copiers, printers, and thelike. More particularly, the invention relates to a sheet-shapedelectrophotographic photoreceptor having excellent adhesiveness to asheet-shaped conductive substrate and also excellent ease of peelingwith a solvent and good electric properties, and an image-formingapparatus having the same mounted thereon.

BACKGROUND OF THE INVENTION

Since instantaneousness and high-quality images are obtained,electrophotography has been used extensively in the fields of on-demandprinters, copiers, various printers, and the like.

As photoreceptors serving as the core of electrophotography, use isbeing made of photoreceptors employing an organic photoconductivematerial which has advantages such as non-polluting properties, ease offilm formation, and ease of production.

Photoreceptors employing an organic photoconductive material include: aso-called dispersion type photoreceptor containing photoconductive fineparticles disperses in a binder resin; and a multilayer typephotoreceptor having superposed layers including a charge-generatinglayer and a charge-transporting layer. The multilayer type photoreceptorhas the following advantages: the multilayer type photoreceptor can beobtained as a high-sensitivity photoreceptor by using acharge-generating material having a high efficiency in combination witha charge-transporting material having a high efficiency; there is a widechoice of material and highly safe photoreceptors are obtained; and,since the photosensitive layer can be easily formed by coating, themultilayer type photoreceptor has high productivity and is advantageousalso in view of cost. Therefore, the multilayer type photoreceptors arethe mainstream of photoreceptors, and have been diligently developed andput to practical use.

Of these, for the reasons that the form is flexible and freedom atdisposition in an apparatus is large, an endless belt-shapedphotoreceptor obtained by linking a sheet-shaped photoreceptor at endparts thereof has been used by preference. Also, for the reasons that aphotoreceptor having a wide area can be easily produced and thephotoreceptor is easily changed inexpensively, a photoreceptor in a formwhere a sheet-shaped photoreceptor is wound on a drum has been used bypreference (e.g., see Patent Documents 1 and 2).

Since the electrophotographic photoreceptor is repeatedly used in anelectrophotographic process, i.e., in a cycle including charging,exposure, development, transfer, cleaning, erase, and the like, thephotoreceptor is deteriorated by various stresses during the process.The deterioration includes such chemical and electrical deteriorationthat strongly acidic ozone and NOx generated from a corona charging unitused as a charging unit cause chemical damage to the photoreceptor and aphotosensitive layer composition is decomposed by the flow of carriersformed by image exposure or erasing light or is decomposed by externallight. Moreover, as deterioration other than the above, there ismechanical deterioration such as wear of the surface of thephotosensitive layer, generation of scratches thereon, and exfoliationof a film caused by sliding with cleaning blades and magnetic brushes,contact with a transfer member or paper, and the like. Also,particularly in the endless belt-shaped photoreceptor, cracks may begenerated on the surface of the photoreceptor owing to flexure andtension generated at the time when the photoreceptor repeatedly passesaround rollers which constitutes a belt unit. In particular, the damagegenerated on the surface of the photosensitive layer is prone to appearon an image and directly impairs quality of the image, so that thedamage becomes a large factor of limiting the life of the photoreceptor.Namely, in order to develop a long-life photoreceptor, it is anessential condition to increase mechanical strength together withenhancement of electrical and chemical durability.

Moreover, the sheet-shaped photoreceptor is difficult to secureadhesiveness between a conductive substrate and the photosensitive layerowing to the flexibility of the photoreceptor, so that there is aconcern of exfoliation of the photosensitive layer.

In the case of a general photoreceptor having no functional layer suchas a surface protective layer, the layer receiving such loads is thephotosensitive layer. The photosensitive layer is usually composed of abinder resin and a photoconductive material, and the binder resinsubstantially determines the strength. However, since the doping amountof the photoconductive material is considerably large, a sufficientmechanical strength has not yet been realized.

As binder resins for the photosensitive layer, use has been made ofvinyl polymers such as poly(methyl methacrylate), polystyrene, andpolyvinyl chloride and copolymers thereof, thermoplastic resins such aspolycarbonate, polyester, polysulfone, phenoxy, epoxy, and siliconeresins, and various thermosetting resins. Of the numerous binder resins,polycarbonate resins have relatively excellent performance and thusvarious polycarbonate resins have hitherto been developed and put topractical use (e.g., see Patent Documents 3 to 6).

DOCUMENT LIST

-   [Patent Document 1] JP-UM-A-6-16966-   [Patent Document 2] JP-A-2000-10315-   [Patent Document 3] JP-A-50-98332-   [Patent Document 4] JP-A-59-71057-   [Patent Document 5] JP-A-59-184251-   [Patent Document 6] JP-A-5-21478

SUMMARY OF THE INVENTION

In the case where an uncoated area is present within the sheet surface,conventional sheet-shaped photoreceptors have a problem that exfoliationstarts from the boundaries and it is an actual state that a binder resinusable for maintaining the adhesiveness between the conductive substrateand the photosensitive layer is limited. Therefore, it is difficult tosecure sufficiently good electrical properties.

Moreover, in the preparation of the uncoated area, there is a case wherea part of a photosensitive layer is peeled with a solvent from aphotoreceptor sheet where the whole area of a sheet-shaped conductivesubstrate is coated with the photosensitive layer. However, the peelingwith the solvent is difficult in some cases depending on the binderresin and this fact has put restrictions on practical use. Since theease of peeling of the photosensitive layer with a solvent is mainlycontrolled by solubility of the binder resin of the photosensitivelayer, selection of the solvent and the binder resin becomes importantbut there is a problem that a resin having low solubility (bisphenol Apolycarbonate resin or the like which is widely used in the sheet-shapeelectrophotographic photoreceptor) is soluble only in solvents havinglow safety (1,4-dioxane and chlorobenzene). Therefore, in thecommercialization, it is a current situation that a material should beselected from resins having high solubility.

The present invention is performed for the purpose of solving suchproblems.

Namely, an object of the invention is to provide a sheet-shapedelectrophotographic photoreceptor which has an uncoated area, is good inmechanical adhesiveness between the photosensitive layer and thesheet-shaped conductive substrate but excellent ease of peeling with asolvent, and is further good in electrical properties.

The present inventors diligently made investigations. As a result, theyhave found that mechanical adhesiveness with the sheet-shaped conductivesubstrate becomes good and on the other hand, ease of peeling with asolvent is excellent, and further good electrical properties areexhibited by incorporating a copolycarbonate resin having an extremelyrestrictive specific structure into the photosensitive layer of thesheet shaped electrophotographic photoreceptor. The invention has beenthus completed.

Namely, the first gist of the invention lies on an electrophotographicphotoreceptor comprising a sheet-shaped conductive substrate and aphotosensitive layer provided thereon, wherein the electrophotographicphotoreceptor contains a photosensitive layer-uncoated area within thesheet surface, and the photosensitive layer contains a copolycarbonateresin having a repeating structure represented by the following generalformula (1):

wherein R¹, R², R³ and R⁴ each independently represent a hydrogen atomor an alkyl group having 4 or less carbon atoms, Z forms a saturatedcyclic aliphatic alkyl group having 5 to 8 carbon atoms including thecarbon atom to be bonded, and the saturated cyclic aliphatic alkyl grouphas one to three methyl groups as substituent(s).

The second gist of the invention lies on the aforementionedelectrophotographic photoreceptor, wherein the copolycarbonate resin isa copolymer of the repeating structure represented by the generalformula (1) above and a repeating structure represented by the followingstructural formula (2):

The third gist of the invention lies on the electrophotographicphotoreceptor, wherein, in the copolycarbonate resin, the molar ratio ofthe repeating structure represented by the structural formula (2) islarger than the molar ratio of the repeating structure represented bythe general formula (1), more preferably lies on the electrophotographicphotoreceptor, wherein the molar ratio of the repeating structurerepresented by the structural formula (2) is twice or more the molarratio of the repeating structure represented by the general formula (1),and also, lies on the electrophotographic photoreceptor, wherein thegeneral formula (1) is represented by the following structural formula(3):

The fourth gist of the invention lies on the electrophotographicphotoreceptor, wherein the thickness of the photosensitive layer is 17μm or larger, and also lies on the electrophotographic photoreceptor,which contains an insulated part within the sheet surface.

The fifth gist of the invention lies on an image-forming apparatuscomprising the aforementioned electrophotographic photoreceptor.

According to the invention, a sheet-shaped electrophotographicphotoreceptor which is good in mechanical adhesiveness between thephotosensitive layer and the sheet-shaped conductive substrate butexcellent ease of peeling with a solvent, and exhibits good electricalproperties, can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual illustration showing one embodiment of theimage-forming apparatus using the electrophotographic photoreceptor ofthe invention.

FIG. 2 is an X-ray diffraction pattern of oxytitanium phthalocyanineused in Examples of the invention.

FIG. 3 is a schematic illustration of the photoreceptor sheet used inExamples of the invention.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   1 Photoreceptor-   2 Charging device (charging roller)-   3 Exposure device-   4 Developing device-   5 Transfer device-   6 Cleaner-   P Recording paper

DETAILED DESCRIPTION OF THE INVENTION

Best modes for carrying out the invention will be explained below indetail. The invention should not be construed as being limited to thefollowing embodiments, and various modifications of the invention can bemade within the spirit of the invention.

The electrophotographic photoreceptor of the invention has asheet-shaped conductive substrate and a photosensitive layer providedthereon, a photosensitive layer-uncoated area is present within thesheet surface, the photosensitive layer contains a polycarbonate resinhaving a specific repeating structure of the invention, and the resin isused as a binder resin of the photosensitive layer to be provided on theconductive substrate of the photoreceptor.

The specific constitution of the photosensitive layer of the inventionincludes a multilayer type photoreceptor formed by superposing, on aconductive substrate, a charge-generating layer including acharge-generating material as a main component and a charge-transportinglayer including a charge-transporting material and a binder resin asmain components; and a dispersion type (single-layer type) photoreceptorhaving a photosensitive layer which is formed on a conductive substrateand which includes a charge-transporting material and a binder resin andcontains a charge-generating material dispersed therein. In theinvention, the polycarbonate resin having a specific repeating structureis used in the photosensitive layer in the single-layer typephotoreceptor, preferably in the charge-transporting layer of themultilayer type photosensitive layer.

<Conductive Substrate>

As the conductive substrate of the invention, one obtained by laminatinga metal layer on an insulated part such as a resin or paper,particularly a biaxially oriented film, is preferred. Materials of thebiaxially oriented film include linear polyester resins such aspolyethylene terephthalate and polybutylene terephthalate, polyolefinresins such as polyethylene and polypropylene, polyvinyl chloride, andthe like. From the standpoints of mechanical strength and dimensionalstability, the linear polyester resins, particularly polyethyleneterephthalate is preferred. The thickness of the film is usually from 30to 150 μm, preferably from 50 to 120 μm, and further preferably from 70to 100 μm.

Moreover, the metal for the metal layer (e.g., metal deposition layer)constituting the conductive substrate includes copper, nickel, zinc,aluminum, ITO (indium-tin oxide), and the like. Of these, aluminum ispreferred. The thickness of the metal layer is usually from about 40 to100 nm. The vapor deposition onto the resin film is performed by a knownvapor-deposition method of the metal, such as electrical heat-meltvapor-deposition method, an ion-beam vapor-deposition method, or an ionplating method.

As the metal layer, use can be made of a metal foil such as an aluminumfoil or a nickel foil or a laminated film obtained by superposing thesemetals. The metal foil in this case preferably has a thickness of 5 μmor less. Also, a conductive material having an appropriate resistancevalue can be further superposed on the metal foil.

The surface of the substrate may be smooth or may have been roughened bymixing particles having a large particle diameter at the time of resinfilm formation.

<Polycarbonate Resin>

The photosensitive layer of the electrophotographic photoreceptor of theinvention contains a copolycarbonate resin having a repeating structurerepresented by the following general formula (1):

wherein in formula (1), R¹, R², R³ and R⁴ each independently represent ahydrogen atom or an alkyl group having 4 or less carbon atoms, Z forms asaturated cyclic aliphatic alkyl group having 5 to 8 carbon atomsincluding the carbon atom to be bonded, and the saturated cyclicaliphatic alkyl group has one to three methyl groups as substituent(s).

Moreover, the polycarbonate resin having the repeating structurerepresented by the above general formula (1) may have a copolymerizationcomponent. As the copolymerization component, a repeating structurerepresented by the following general formula (2) is preferred.Furthermore, the above general formula (1) is preferably represented bythe following structural formula (3).

Moreover, the polycarbonate resin having the repeating structurerepresented by the above general formula (1) is particularly preferablyrepresented by the following general formula (4). With regard to m andn, m is preferably less than n and further, 2m is preferably equal to orless than n.

The polycarbonate resin of the invention can be used in theelectrophotographic photoreceptor as a mixture with other resin(s). Theresins to be used in combination include vinyl polymers such aspoly(methyl methacrylate), polystyrene, and polyvinyl chloride andcopolymers thereof, thermoplastic resins such as polycarbonate,polyester, polyesterpolycarbonate, polysulfone, phenoxy, epoxy, andsilicone resins, and various thermosetting resins. Of these resins,polycarbonate resins and polyarylate resins are preferred.

The mixing ratio of the resins to be used in combination is notparticularly limited but, in order to obtain the advantage of theinvention sufficiently, the other resins are preferably used within therange not exceeding the ratio of the polycarbonate resin of theinvention and particularly, the other resins are preferably not used incombination.

<Undercoat Layer>

An undercoat layer may be disposed between the conductive substrate andthe photosensitive layer in order to improve adhesiveness, nonblockingproperties, etc.

As the undercoat layer, use may be made of a resin, a material obtainedby dispersing particles of a metal oxide in a resin, or the like.Examples of the metal oxide particles for use in the undercoat layerinclude particles of a metal oxide containing one metallic element, suchas titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, zincoxide, or iron oxide, and particles of a metal oxide containing two ormore metallic elements, such as calcium titanate, strontium titanate, orbarium titanate. Metal oxide particles of one kind only may be used, ora mixture of two or more kinds of metal oxide particles may be used.Preferred of these particulate metal oxides are titanium oxide andaluminum oxide. Particularly preferred is titanium oxide. The titaniumoxide particles may be ones in which the surface thereof has undergone atreatment with an inorganic substance, e.g., tin oxide, aluminum oxide,antimony oxide, zirconium oxide, or silicon oxide, or with an organicsubstance, e.g., stearic acid, a polyol, or a silicone. The crystal formof the titanium oxide particles may be any of rutile, anatase, brookite,and amorphous. Two or more crystalline states may be included.

With respect to particle diameter, metal oxide particles having variousparticle diameters can be used. However, metal oxide particles having aparticle diameter of from 10 nm to 100 nm in terms of averageprimary-particle diameter are preferred from the standpoints ofproperties and liquid stability. Particularly preferred are metal oxideparticles having a particle diameter of from 10 nm to 50 nm.

It is desirable that an undercoat layer should be formed so as to beconstituted of a binder resin and metal oxide particles dispersed in theresin. As the binder resin for use in the undercoat layer, use may bemade of a phenoxy, epoxy, polyvinylpyrrolidone, poly(vinyl alcohol),casein, poly(acrylic acid), cellulose derivative, gelatin, starch,polyurethane, polyimide, polyamide, or the like. Such a polymer can beused alone or in a cured form obtained with a curing agent. Of these, analcohol-soluble copolyamide, modified polyamide, or the like ispreferred because such polyamides show satisfactory dispersibility andapplicability.

The proportion of the inorganic particles to be added to the binderresin can be selected at will. However, from the standpoints of thestability and applicability of the dispersion, it is preferred to usethe inorganic particles in an amount ranging from 10 parts by weight to500 parts by weight per 100 parts by weight of the binder resin.

The thickness of the undercoat layer can be selected at will. However,the thickness thereof is preferably from 0.1 μm to 25 μm from thestandpoints of photoreceptor characteristics and applicability. A knownantioxidant and the like may be added to the undercoat layer.

<Charge-Generating Layer>

In the case where the electrophotographic photoreceptor of the inventionis of the multilayer type, examples of charge-generating materialsusable in the charge-generating layer thereof include variousphotoconductive materials such as selenium and alloys thereof, cadmiumsulfide, and other inorganic photoconductive materials, and organicpigments including phthalocyanine pigments, azo pigments, quinacridonepigments, indigo pigments, perylene pigments, polycyclic quinonepigments, anthanthrone pigments, and benzimidazole pigments. Of these,organic pigments are preferred. In particular, phthalocyanine pigmentsand azo pigments are preferred. Particles of these charge-generatingmaterials are used in the state of being bound with various binderresins such as, e.g., polyester resins, poly(vinyl acetate),poly(acrylic ester)s, poly(methacrylic ester)s, polyesters,polycarbonates, poly(vinyl acetoacetal), poly(vinyl propional),poly(vinyl butyral), phenoxy resins, epoxy resins, urethane resins,cellulose esters, and cellulose ethers. In this case, acharge-generating material may be used in such a proportion that theamount of the charge-generating material is in the range of from 30parts by weight to 500 parts by weight per 100 parts by weight of thebinder resin. A suitable film thickness of the charge-generating layeris generally from 0.1 μm to 1 μm, preferably from 0.15 μm to 0.6 μm.

In the case where a phthalocyanine compound is used as acharge-generating material, use may be made of metal-freephthalocyanines and phthalocyanine compounds to which a metal, e.g.,copper, indium, gallium, tin, titanium, zinc, vanadium, silicon, orgermanium, or an oxide, halide, or another form of the metal hascoordinated. Examples of ligands for metal atoms having a valence of 3or higher include, in addition to an oxygen atom and a chlorine atomshown above, a hydroxyl group and an alkoxy group. Especially suitableare X-form and τ-form metal-free phthalocyanines, which have highsensitivity, A-form, B-form, D-form, and other titanyl phthalocyanines,vanadyl phthalocyanines, chloroindium phthalocyanines, chlorogalliumphthalocyanines, and hydroxygallium phthalocyanines. Of the crystalforms of titanyl phthalocyanines shown above, the A-form and B-form werereferred to as I-phase and II-phase, respectively, by W. Heller et al.(Zeit. Kristallogr., 159 (1982) 173), and the A-form is known as astable form. The D-form is a crystal form characterized by showing adistinct peak at a diffraction angle 2θ±0.2° of 27.3° in powder X-raydiffractometry using a CuKα line. A single phthalocyanine compound maybe used alone, or some phthalocyanine compounds may be used in the stateof being mixed with each other. In the case where phthalocyaninecompounds are to be used in a mixed state, the constituent elements maybe mixed later together and used. Alternatively, the phthalocyaninecompounds may be ones the mixed state of which was generated in aproduction/treatment step of the phthalocyanine compounds, such as,e.g., synthesis, pigment formation, or crystallization. Known as suchtreatments are an acid paste treatment, grinding, solvent treatment, andthe like.

<Charge-Transporting Layer>

The charge-transporting layer of the multilayer type photoreceptorcontains a charge-transporting material and also usually contains thebinder resin and other component(s) that may be used as needed. Thecharge-transporting layer may be specifically obtained as follows. Forexample, the charge-transporting material and the like and the binderresin are dissolved or dispersed in a solvent to prepare a coatingfluid, which is then applied onto a charge-generating layer in the caseof a normal multilayer type photosensitive layer or applied on aconductive substrate (on an undercoat layer in the case where theundercoat layer is provided) in the case of a reverse multilayer typephotosensitive layer, followed by drying.

The charge-transporting material is not particularly limited and anymaterial can be used. Examples of known charge-transporting materialsinclude electron-attracting materials such as aromatic nitro compounds,e.g., 2,4,7-trinitrofluorenone, cyano compounds, e.g.,tetracyanoquinodimethane, and quinone compounds, e.g., diphenoquinone,heterocyclic compounds such as carbazole derivatives, indolederivatives, imidazole derivatives, oxazole derivatives, pyrazolederivatives, thiadiazole derivatives, and benzofuran derivatives, andelectron-donating materials such as aniline derivatives, hydrazonederivatives, aromatic amine derivatives, stilbene derivatives, butadienederivatives, enamine derivatives, compounds constituted of two or moreof these compounds bonded to each other, and polymers having, in themain chain or side chains thereof, a group derived from any of thesecompounds. Preferred of these are carbazole derivatives, aromatic aminederivatives, stilbene derivatives, butadiene derivatives, enaminederivatives, and compounds composed of two or more of these compoundsbonded to each other. Any one of these charge-transporting materials maybe used alone or two or more thereof may be used in any combination.

Specific examples of preferred structures of the charge-transportingmaterial are shown below. These specific examples are shown forillustration and any known charge-transporting materials may be usedunless they depart from the gist of the invention.

Such charge-transporting material is bound with a binder resin includinga polycarbonate resin of the invention to form a charge-transportinglayer. The charge-transporting layer may be composed of a single layer,or may be composed of superposed layers differing in component orcomposition.

The proportion of the charge-transporting material to the binder resinis usually from 30 to 200 parts by weight, preferably from 40 to 150parts by weight per 100 parts by weight of the binder resin. The effectof the use of the polycarbonate resin according to the invention becomesremarkable particularly when the proportion of the charge-transportingmaterial is small. The charge-transporting material is used in aproportion of preferably 65 parts by weight or smaller, more preferably55 parts by weight or smaller, and further preferably 45 parts by weightor smaller per 100 parts by weight of the binder resin.

The film thickness of the charge-transporting layer may be generallyfrom 5 to 50 μm, preferably from 10 to 45 μm but the effect of the useof the polycarbonate resin according to the invention becomes remarkableparticularly when the thickness is 17 μm or larger.

Well-known additives such as a plasticizer, an antioxidant, anultraviolet absorber, an electron-attracting compound, a dye, a pigment,and a leveling agent may be incorporated into the charge-transportinglayer in order to improve film-forming properties, flexibility,applicability, fouling resistance, gas resistance, light resistance,etc. Examples of the antioxidant include hindered phenol compounds andhindered amine compounds. Examples of the dye and pigment includevarious colorant compounds and azo compounds.

<Dispersion Type (Single-Layer Type) Photosensitive Layer>

In the case of dispersion type photosensitive layer, thecharge-generating material described above is dispersed in acharge-transporting medium having a composition such as that shownabove.

In this case, it is necessary that the charge-generating material shouldhave a sufficiently small particle diameter and the charge-generatingmaterial is used in a particle diameter of preferably 1 μm or smaller,more preferably 0.5 μm or smaller. In the case where the amount of thecharge-generating material to be dispersed in the photosensitive layeris too small, sufficient sensitivity is not obtained. Too large amountsthereof exert an adverse influence to result in a decrease inelectrification characteristics, decrease in sensitivity, etc. Forexample, the charge-generating material is used in an amount preferablyin the range of from 0.5 to 50% by weight, more preferably in the rangeof from 1 to 20% by weight.

The thickness of the photosensitive layer is generally from 5 to 50 μm,more preferably from 10 to 45 μm. In this case also, a remarkable effectis obtained in the case where the thickness is 17 μm or larger. Also inthis case, a known plasticizer for improving film-forming properties,flexibility, mechanical strength, etc., an additive for reducingresidual potential, a dispersion aid for improving dispersion stability,a leveling agent or surfactant for improving applicability, and otheradditives such as, e.g., a silicone oil or fluorochemical oil may havebeen added.

A protective layer may be formed on the photosensitive layer for thepurposes of preventing the photosensitive layer from wearing and ofpreventing/diminishing the deterioration of the photosensitive layercaused by, e.g., a product of discharge generated from charging units,etc.

A surface layer may contain a fluororesin, silicone resin, or the likefor the purpose of reducing the frictional resistance or wear of thephotoreceptor surface. The surface layer may contain particles of any ofthese resins or particles of an inorganic compound.

<Measurement Method of Film Thickness of Photosensitive Layer>

The film thickness of the photosensitive layer can be measured by thefollowing method.

In the photoreceptor sheet coated by a known method, the thickness ofthe substrate is first measured using a starting part of coating or anend part of coating. Namely, the photosensitive layer is peeled offusing a solvent capable of dissolving the photosensitive layer(generally, a solvent used at coating). On this occasion, when anundercoat layer is present, the solvent is necessarily a solvent whichdoes not dissolve the underlying layer. In the case of the single-layertype photoreceptor, the photosensitive layer is peeled as it is. In thecase of the double-layer type photoreceptor where the charge-generatinglayer and the charge-transporting layer are superposed, both of the twolayers are peeled off. The peeled part can be detected as the thicknessof the conductive substrate (including the undercoat layer when theundercoat layer is present).

On the other hand, with regard to the part on which the photosensitivelayer is coated, the thickness of the whole sheet is measured on any tenpoints including the width direction of coating and the travelingdirection of coating and an average value is calculated. The thicknessof the photosensitive layer can be determined by subtracting thethickness of the substrate (+undercoat layer) determined beforehand fromthe thickness of the whole sheet.

Namely, the thickness of the photosensitive layer is defined as thethickness of the photosensitive layer itself in the case of thesingle-layer type photoreceptor and as the thickness of the two layersin the case of the double-layer type photoreceptor.

Incidentally, the measurement can be performed using a gauge head havinga diameter of 2 mm on a digital electronic micrometer (K351C model,manufactured by Anritsu Corporation) but any other known film thicknessmeasurement methods may be used.

<Method of Preparing Electrophotographic Photoreceptor>

The method of preparing an electrophotographic photoreceptor to whichthe present embodiment is to be applied is not particularly limited.Usually, individual layers constituting the photoreceptor may be formedby application on a conductive substrate by a known technique such asdie coating, reverse coating, gravure coating, bar coating, or the likeknown as methods of forming a photosensitive layer of a sheet-shapedelectrophotographic photoreceptor.

As forming methods of individual layers, known methods includingsuccessively applying coating fluids obtained by dissolving ordispersing in a solvent the materials to be incorporated into layers.

The photoreceptor after coating is subjected to a drying step until thesolvent in the coated film is substantially evaporated and removed. Asthe drying method, any method hitherto known and performed can beapplied and, for example, drying may be performed by a heating roller, ahot-air dryer, the above-described dryer, an infrared dryer, and/or afar infrared dryer. The drying temperature is usually in the range of 60to 140° C.

The sheet-shaped photoreceptor thus obtained is used as an endless beltafter both end parts thereof are linked by a known method such asultrasonic fusion following a step of cutting the photoreceptor into anappropriate size as needed or is used as it is with winding it on adrum. In the case of winding it on a drum, a roll rolled thinly may bestored inside the drum and is wound off or one sheet thereof may bewound on the drum.

In the case of either form, a conductive layer may be provided for earthconnection but, in the invention, an exposed uncoated area of thephotosensitive layer is present instead of the conductive layer withinthe surface of the photoreceptor sheet. The uncoated area is usuallyformed at the end parts within the sheet surface.

<Ease of Peeling with Solvent>

In the case where the sheet-shaped photoreceptor is formed by a knowncoating method, coating is performed with winding off the conductivesubstrate wound into a roll shape and then the coated photoreceptor iscut out, so that it is difficult to apply the photosensitive layer onlya part of the conductive substrate and hence the whole area of the sheetunavoidably becomes the photosensitive layer. Therefore, in order toobtain the photosensitive layer-uncoated part for ground connection, itis necessary to form the uncoated area by post-processing. Thus, it isnecessary to peel the photosensitive layer, e.g., by a peeling solvent,in order to form the uncoated area by post-processing. At that time, theeasiness of peeling of the photosensitive layer becomes important.

In the invention, a peeling solvent for use at the formation of theuncoated area is acetone, tetrahydrofuran, or the like from theviewpoint of safety. These may be used alone or two or more thereof maybe used in combination. Moreover, 1,4-dioxane, chlorobenzene, or thelike is effective for hardly soluble resins, for example, a bisphenol Apolycarbonate resin and the like which are widely used in sheet-shapedelectrophotographic photoreceptors but there is a concern of causing asafety problem.

<Image-Forming Apparatus>

The embodiment of the image-forming apparatus using theelectrophotographic photoreceptor of the invention is explained below byreference to FIG. 1, which illustrates the constitution of importantparts of the apparatus. However, embodiments thereof should not beconstrued as being limited to those explained below, and the apparatuscan be modified at will so long as the modifications do not depart fromthe gist of the invention.

As shown in FIG. 1, the image-forming apparatus includes anelectrophotographic photoreceptor 1, a charging device 2, an exposuredevice 3, and a developing device 4, and the apparatus may further has atransfer device 5, a cleaner 6, and a fixing device (not shown in thefigure) according to need.

The electrophotographic photoreceptor 1 is not particularly limited sofar as it is any of the electrophotographic photoreceptors of theinvention described above, FIG. 1 shows, as an example thereof, anendless belt-shaped photoreceptor composed of a sheet-shaped conductivesubstrate and, formed on the surface thereof, the photosensitive layerdescribed above and transformed into an endless belt shape by ultrasonicfusion. The charging device 2, exposure device 3, developing device 4,transfer device 5, and cleaner 6 have been disposed along the peripheralsurface of this electrophotographic photoreceptor 1.

The charging device 2 serves to charge the electrophotographicphotoreceptor 1. It evenly charges the surface of theelectrophotographic photoreceptor 1 to a given potential. FIG. 1 shows acorona charging device (corotron) as an example of the charging device2. Besides the device, corona charging devices such as scorotrons,contact type charging devices such as charging rollers and chargingbrushes, and the like are frequently used.

In many cases, the electrophotographic photoreceptor 1 and the chargingdevice 2 have been designed to constitute a cartridge (hereinaftersuitably referred to as “photoreceptor cartridge”) which involves thesetwo members and is designed to be removable from the main body of theimage-forming apparatus. When, for example, the electrophotographicphotoreceptor 1 and the charging device 2 have deteriorated, thisphotoreceptor cartridge can be removed from the main body of theimage-forming apparatus and a fresh photoreceptor cartridge can bemounted in the main body of the image-forming apparatus. Also withrespect to the toner, which will be described later, the toner in manycases has been designed to be stored in a toner cartridge and beremovable from the main body of the image-forming apparatus. When thetoner in the toner cartridge in use has run out, this toner cartridgecan be removed from the main body of the image-forming apparatus and afresh toner cartridge can be mounted. Furthermore, there are cases wherea cartridge including all of the electrophotographic photoreceptor 1, acharging device 2, and a toner is used. Moreover, theelectrophotographic photoreceptor 1, a charging device 2 areincorporated into a larger-scale on-demand printing apparatus in somecases.

The exposure device 3 is not particularly limited in kind so long as itcan illuminate the electrophotographic photoreceptor 1 and thereby forman electrostatic latent image in the photosensitive surface of theelectrophotographic photoreceptor 1. Specific examples thereof includehalogen lamps, fluorescent lamps, lasers such as semiconductor lasersand He—Ne lasers, and LEDs. It is also possible to conduct exposure bythe technique of internal photoreceptor exposure. Although any desiredlight can be used for exposure, for example, a monochromatic lighthaving a wavelength of 780 nm or 830 nm, a monochromatic light having aslightly short wavelength of 600 to 700 nm, a monochromatic light havinga short wavelength of 380 to 500 nm, a white light after passing througha suitable filter, or the like may be used to conduct exposure.

The developing device 4 is not particularly limited in kind and anydevices such as ones operated by a dry development technique, e.g.,cascade development, development with one-component conductive toner, ortwo-component magnetic brush development, a wet development technique,etc. can be used.

The kind of the toner is arbitrary and other than a powder toner, notonly a polymerization toner obtained by using suspension polymerizationor emulsion polymerization can be used but also a liquid toner can beused in an on-demand printer. Particularly, in the case where thepolymerization toner is used, one having such a small particle diameteras about 4 to 8 μm is preferred and, with regard to the shape of thetoner particle, various ones from nearly spherical one to potato-likeone which is out of spherical one can be used. The polymerization toneris excellent in charging evenness and transferring ability and hence issuitably used for high-definition imaging. The liquid toner can beformed into a diameter of from 1 to 3 μm and is suitable for more highlyfine image output.

The transfer device 5 is not particularly limited in kind, and use canbe made of a device operated by any desired technique selected from anelectrostatic transfer technique, pressure transfer technique, adhesivetransfer technique, and the like, such as corona transfer, rollertransfer, and belt transfer. Here, the transfer device 5 is one composedof a transfer charger, transfer roller, transfer belt, or the likedisposed so as to face the electrophotographic photoreceptor 1. A givenvoltage (transfer voltage) which has the polarity opposite to that ofthe charge potential of the toner is applied to the transfer device 5,and this transfer device 5 thus transfers the toner image formed on theelectrophotographic photoreceptor 1 to a recording paper (paper ormedium) P.

The cleaner 6 is not particularly limited, and any desired cleaner canbe used, such as a brush cleaner, magnetic brush cleaner, electrostaticbrush cleaner, magnetic roller cleaner, or blade cleaner. The cleaner 6serves to scrape off the residual toner adherent to the photoreceptor 1with a cleaning member and thus recover the residual toner.

The toner which has been transferred to the recording paper P is heatedto a molten state during the passage through a fixing device. After thepassage, the toner is cooled and fixed to the recording paper P.

The fixing device also is not particularly limited in kind. Fixingdevices which can be mounted include ones operated by any desired fixingtechnique, such as heated-roller fixing, flash fixing, oven fixing, orpressure fixing.

In the image-forming apparatus having the constitution described above,image recording is conducted in the following manner. First, the surface(photosensitive surface) of the photoreceptor 1 is charged to a givenpotential (e.g., −600 V) by the charging device 2. This charging may beconducted with a direct-current voltage or with a direct-current voltageon which an alternating-current voltage has been superimposed.

Subsequently, the charged photosensitive surface of the photoreceptor 1is exposed by the exposure device 3 according to the image to berecorded. Thus, an electrostatic latent image is formed in thephotosensitive surface. This electrostatic latent image formed in thephotosensitive surface of the photoreceptor 1 is developed by thedeveloping device 4.

When the charged toner held on the developing roller 4 comes intocontact with the surface of the photoreceptor 1, a toner imagecorresponding to the electrostatic latent image is formed on thephotosensitive surface of the photoreceptor 1. This toner image istransferred to a recording paper P by the transfer device 5. Thereafter,the toner which has not been transferred and remains on thephotosensitive surface of the photoreceptor 1 is removed by the cleaner6.

After the transfer of the toner image to the recording paper P, thisrecording paper P is passed through the fixing device 7 to thermally fixthe toner image to the recording paper P. Thus, a finished image isobtained.

Incidentally, the image-forming apparatus may have a constitution inwhich an erase step, for example, can be conducted, in addition to theconstitution described above. The erase step is a step in which theelectrophotographic photoreceptor is exposed to a light to thereby erasethe residual charges from the electrophotographic photoreceptor. As aneraser, there may be used a fluorescent lamp, LED, or the like. Thelight to be used in the erase step, in many cases, is a light havingsuch an intensity that the exposure energy thereof is at least 3 timesthe energy of the exposure light.

The constitution of the image-forming apparatus may be further modified.For example, the apparatus may have a constitution in which steps suchas a pre-exposure step and an auxiliary charging step can be conducted,or have a constitution in which offset printing is conducted.Furthermore, the apparatus may have a full-color tandem constitutionemploying two or more toners. Particularly, the endless belt-shapedphotoreceptor is suitable for four-cycle full-color printing in whichcolor images of individual colors are repeatedly developed.

EXAMPLES

The embodiment will be explained below more specifically with referenceto Examples. The following Examples are given in order to explain theinvention in detail, and the invention should not be construed as beinglimited to the following Examples unless the invention departs from thespirit thereof. Each “parts” described in the following Examples andComparative Examples means “parts by weight” unless otherwise indicated.

The measurement of the viscosity-average molecular weight of the binderresin is explained here.

A resin is dissolved in dichloromethane to prepare a solution having aconcentration C of 6.00 g/L. Using an Ubbelohde capillary viscometerhaving a solvent (dichloromethane) flow time t₀ of 136.16 seconds, thesample solution is investigated for flow time t in a thermostatic waterbath set at 20.0° C. The viscosity-average molecular weight Mv iscalculated according to the following equations.

a=0.438×η_(sp)+1 η_(sp) =t/t ₀−1

b=100×η_(sp) /C C=6.00 (g/L)

η=b/a

Mv=3207×η^(1.205)

<Production of Photoreceptor Sheet> Example 1

Rutile titanium oxide having an average primary-particle diameter of 40nm (“TTO55N” manufactured by Ishihara Sangyo Kaisha, Ltd.) andmethyldimethoxysilane (“TSL8117” manufactured by Toshiba Silicone Co.,Ltd.) in an amount of 3% by weight based on titanium oxide were chargedinto a high-speed fluidized mixing kneader (“SMG300” manufactured byKawata MFG Co., Ltd.). A surface treated titanium oxide obtained byhigh-speed mixing at a rotation peripheral speed of 34.5 msec wasdispersed in a mixed solvent of methanol/1-propanol with a ball mill tothereby form a dispersion slurry of hydrophobized titanium oxide. Thisdispersion slurry was mixed with a mixed solvent ofmethanol/1-propanol/toluene and with pellets of a copolyamide composedof ε-caprolactam [compound represented by the following formula(A)]/bis(4-amino-3-methylcyclohexyl)methane [compound represented by thefollowing formula (B)]/hexamethylenediamine [compound represented by thefollowing formula (C)]/decamethylenedicarboxylic acid [compoundrepresented by the following formula (D)]/octadecamethylenedicarboxylicacid [compound represented by the following formula (E)] in acomposition molar ratio of 60%/15%/5%/15%/5% with stirring under heatingto dissolve the polyamide pellets. Thereafter, the resultant mixture wassubjected to an ultrasonic dispersion treatment to thereby form adispersion for undercoat layer having a solid concentration of 18.0%which contained methanol/1-propanol/toluene in a weight ratio of 7/1/2and the hydrophobized titanium oxide/the copolyamide in a weight ratioof 3/1.

The coating fluid for undercoat layer formation thus obtained wasapplied with a wire bar onto an aluminum-deposited polyethyleneterephthalate (thickness: 75 μm) and dried to form an undercoat layer ina thickness of 1.2 μm on a dry basis.

Then, 10 parts by weight of oxytitanium phthalocyanine showing a strongdiffraction peak at a Bragg angle (2θ±0.2) of 27.3° in X-raydiffractometry using a CuKα line and having the powder X-ray diffractionspectrum shown in FIG. 2 was added to 150 parts by weight of1,2-dimethoxyethane and subjected to a pulverization/dispersiontreatment with a sand grinding mill to form a pigment-dispersed fluid.To 160 parts by weight of the pigment-dispersed fluid thus obtained wasadded 100 parts by weight of a 5% 1,2-dimethoxyethane solution ofpoly(vinyl butyral) (trade name #6000C manufactured by Denki KagakuKogyo K.K.) and an appropriate amount of 1,2-dimethoxyethane to finallyprepare a dispersion having a solid concentration of 4.0%.

The dispersion was applied on the aforementioned undercoat layer with awire bar and then dried to form a charge-generating layer in a thicknessof 0.4 μm on a dry basis.

Then, 40 parts by weight of a charge-transporting material of ahydrazone compound shown below, 100 parts by weight of the polycarbonateresin (viscosity-average molecular weight: 22,000) according to theinvention composed of the repeating unit (1-1), 0.05 parts by weight ofa silicone oil as a leveling agent were mixed into 640 parts by weightof a mixed solvent of tetrahydrofuran and toluene (tetrahydrofuran: 70%by weight, toluene: 30% by weight) to prepare a coating fluid forcharge-transporting-layer formation.

The polycarbonate resin was a resin commercially available as a tradename “APEC” from Bayer AG and was used as it was received withoutpurification.

The fluid was applied on the aforementioned charge-generating layer withan applicator in a thickness of 20 μm on a dry basis and then dried at125° C. for 20 minutes to form a charge-transporting layer, therebypreparing a photoreceptor sheet A1.

The photoreceptor sheet A1 was cut into a size of 100 mm×251 mm and usedfor measurement of electrical properties. Also, another sheet of thesame one was prepared and the end parts were peeled off with acetone andethanol to obtain a sample having an uncoated area of 100 mm×100 mm,which was used for adhesion strength test.

Example 2

A photoreceptor sheet B1 was produced in the same manner as in Example1, except that the polycarbonate resin composed of the repeating unit(1-1) used in the coating fluid for charge-transporting-layer formationof Example 1 was changed to a polycarbonate resin (viscosity-averagemolecular weight: 22,000) composed of a repeating unit (1-2) having thefollowing structure.

Comparative Example 1

A photoreceptor sheet C1 was produced in the same manner, except thatthe polycarbonate resin composed of the repeating unit (1-1) used in thecoating fluid for charge-transporting-layer formation of Example 1 waschanged to a polycarbonate resin (viscosity-average molecular weight:20,000) only composed of a repeating unit (3) having the followingstructure.

Comparative Example 2

It was intended to produce a photoreceptor sheet in the same manner asin Example 1 except that the polycarbonate resin composed of therepeating unit (1-1) used in the coating fluid forcharge-transporting-layer formation of Example 1 was changed to apolycarbonate resin (viscosity-average molecular weight: 30,000)composed of a repeating unit (bisphenol A) having the followingstructure but the resin was not dissolved in the mixed solution oftetrahydrofuran/toluene. Therefore, the solvent was changed to 100%1,4-dioxane and a photoreceptor sheet D1 was produced.

Moreover, also at the preparation of a sheet for adhesiveness test,since peeling was difficult with acetone, 1,4-dioxane was used also as apeeling solvent.

Comparative Example 3

A photoreceptor sheet E1 was produced in the same manner, except thatthe polycarbonate resin composed of the repeating unit (1-1) used in thecoating fluid for charge-transporting-layer formation of Example 1 waschanged to a polycarbonate resin (viscosity-average molecular weight:20,000) only composed of a repeating unit (bisphenol Z) having thefollowing structure.

Comparative Example 4

It was intended to produce a photoreceptor sheet in the same manner asin Example 1 except that the polycarbonate resin composed of therepeating unit (1-1) used in the coating fluid forcharge-transporting-layer formation of Example 1 was changed to amixture of 33 parts of a polycarbonate resin (viscosity-averagemolecular weight: 20,000) only composed of a repeating unit (3) havingthe following structure and 67 parts of a polycarbonate resin(viscosity-average molecular weight: 30,000) composed of a repeatingunit (bisphenol A) having the following structure but the resin was notdissolved in the mixed solution of tetrahydrofuran/toluene. Therefore,the solvent was changed to 100% 1,4-dioxane and a photoreceptor sheet F1was produced.

Moreover, also at the preparation of a sheet for adhesiveness test,since peeling was difficult with acetone, 1,4-dioxane was used also as apeeling solvent.

Example 3

A photoreceptor sheet A2 was obtained in the same manner as in Example 1except that the film thickness of the photosensitive layer was 13 μm.

Example 4

A photoreceptor sheet B2 was obtained in the same manner as in Example 2except that the film thickness of the photosensitive layer was 13 μm.

Comparative Example 5

A photoreceptor sheet C2 was obtained in the same manner as inComparative Example 1 except that the film thickness of thephotosensitive layer was 13 μm.

Comparative Example 6

A photoreceptor sheet D2 was obtained in the same manner as inComparative Example 2 except that the film thickness of thephotosensitive layer was 13 μm.

Comparative Example 7

A photoreceptor sheet E2 was obtained in the same manner as inComparative Example 3 except that the film thickness of thephotosensitive layer was 13 μm.

Comparative Example 8

A photoreceptor sheet F2 was obtained in the same manner as inComparative Example 4 except that the film thickness of thephotosensitive layer was 13 μm.

Reference Example 1

The coating fluid for undercoat layer formation obtained in Example 1was applied onto a non-anodized aluminum cylinder (outer diameter: 80mm, length: 350 mm, thickness: 1 mm) by dipping it to the position of320 mm from the lower end of the cylinder to form an undercoat layer ina thickness of 1.2 μm on a dry basis.

Then, the aluminum cylinder on which the undercoat layer had beenprovided was dipped into the pigment-dispersed fluid of oxytitaniumphthalocyanine obtained in Example 1 to the position of 320 mm from thelower end of the cylinder to apply the fluid, thereby forming acharge-generating layer in a thickness of 0.4 μm on a dry basis.

Furthermore, the coating fluid for charge-transporting-layer formationobtained in Example 1 was applied onto the aforementionedcharge-generating layer by dipping the cylinder to the position of 320mm from the lower end thereof in a thickness of 20 μm on a dry basis,thereby obtaining a photoreceptor drum G1 having a multilayer typephotosensitive layer.

Two pieces of the same drum were produced and one drum was used for theelectrical property test and another one for the adhesiveness test.Since the dip coating method was used, an uncoated area could be formedwithout peeling with a solvent.

Reference Example 2

A photoreceptor drum H1 was produced in the same manner as in ReferenceExample 1, except that the polycarbonate resin composed of the repeatingunit (1-1) used in the coating fluid for charge-transporting-layerformation of Reference Example 1 was changed to a polycarbonate resin(viscosity-average molecular weight: 22,000) composed of a repeatingunit (1-2) having the following structure.

Reference Example 3

A photoreceptor drum I1 was produced in the same manner as in ReferenceExample 1, except that the polycarbonate resin composed of the repeatingunit (1-1) used in the coating fluid for charge-transporting-layerformation of Reference Example 1 was changed to a polycarbonate resin(viscosity-average molecular weight: 20,000) only composed of arepeating unit (3) having the following structure.

Reference Example 4

It was intended to produce a photoreceptor drum in the same manner as inReference Example 1 except that the poly carbonate resin composed of therepeating unit (1-1) used in the coating fluid forcharge-transporting-layer formation in Reference Example 1 was changedto a polycarbonate resin (viscosity-average molecular weight: 30,000)composed of a repeating unit (bisphenol A) having the followingstructure but the resin was not dissolved in the mixed solution oftetrahydrofuran/toluene. Therefore, the solvent was changed to 100%1,4-dioxane and a photoreceptor drum J1 was produced.

Reference Example 5

A photoreceptor drum K1 was produced in the same manner, except that thepolycarbonate resin composed of the repeating unit (1-1) used in thecoating fluid for charge-transporting-layer formation of ReferenceExample 1 was changed to a polycarbonate resin (viscosity-averagemolecular weight: 20,000) only composed of a repeating unit (bisphenolZ) having the following structure.

Reference Example 6

It was intended to produce a photoreceptor drum in the same manner as inExample 1 except that the polycarbonate resin composed of the repeatingunit (1-1) used in the coating fluid for charge-transporting-layerformation in Reference Example 1 was changed to a mixture of 33 parts ofa polycarbonate resin (viscosity-average molecular weight: 20,000) onlycomposed of a repeating unit (3) having the following structure and 67parts of a polycarbonate resin (viscosity-average molecular weight:30,000) composed of a repeating unit (bisphenol A) having the followingstructure but the resin was not dissolved in the mixed solution oftetrahydrofuran/toluene. Therefore, the solvent was changed to 100%1,4-dioxane and a photoreceptor drum L1 was produced.

For the photoreceptor sheets A1, B1, C1, D1, E1, F1, A2, B2, C2, D2, E2,and F2 and photoreceptor drums G1, H1, I1, J1, K1, and L1 produced, thefollowing electrical property test and adhesiveness test were performed.The results are summarized in Table 1.

<Electrical Property Test>

Using an apparatus for electrophotographic-property evaluation producedin accordance with the measurement standards adopted by the Society ofElectrophotography of Japan (described in Zoku Denshishashin Gijutsu NoKiso To Oyo, edited by the Society of Electrophotography of Japan,Corona Publishing Co., Ltd., pp. 404-405), after each of thephotoreceptor sheets A1 to F2 was attached to an aluminum-made drumhaving a diameter of 80 mm to form a cylindrical one and thealuminum-made drum was electrically connected to the aluminum substrateof the photoreceptor sheet, each of the cylindrical ones and thephotoreceptor drums G1 to L1 as they were was rotated at a constantrotation speed of 60 rpm and subjected to an electrical propertyevaluation test in which a cycle including charging, exposure, potentialmeasurement, and erase was conducted. In this test, the photoreceptorwas charged so as to result in an initial surface potential of −700 V,and exposed at 1.0 μJ/cm² to the monochromatic light of 780 nm obtainedby converting the light from a halogen lamp with an interference filter.At 180 milliseconds after the exposure, the surface potential(hereinafter sometimes referred to as VL) was measured. This measurementwas made in an environment having a temperature of 25° C. and a relativehumidity of 50%.

<Adhesiveness Test>

Adhesiveness of the photosensitive layer was tested by cutting anadhesive cellophane tape (manufactured by Nichiban Co., Ltd.) into alength of 100 mm and attaching it on the photosensitive layer part overa length of 50 mm and the uncoated part over a length, of 30 mm in thephotoreceptor sheet or the photoreceptor drum having the uncoated areaand lifting up the tape slantwise at an angle of 45° with holding thetape at remaining 20 mm length part (which continued to the partattached to the uncoated part).

TABLE 1 Film Electrical thickness property VL Resin unit CTM μm −VAdhesiveness Example 1 A1 (1-1) Hydrazone 20 60 Good 2 B1 (1-2) idem 2058 Good 3 A2 (1-1) idem 13 35 Good 4 B2 (1-2) idem 13 34 GoodComparative 1 C1 (3) idem 20 60 Bad Example 2 D1 Bisphenol A idem 20 75Good 3 E1 Bisphenol Z idem 20 72 Medium 4 F1 (3)/bis A idem 20 70 Medium5 C2 (3) idem 13 35 Medium 6 D2 Bisphenol A idem 13 43 Good 7 E2Bisphenol Z idem 13 42 Good 8 F2 (3)/bis A idem 13 40 Medium Reference 1G1 (1-1) idem 20 59 Good Example 2 H1 (1-2) idem 20 59 Good 3 I1 (3)idem 20 58 Good 4 J1 Bisphenol A idem 20 74 Good 5 K1 Bisphenol Z idem20 72 Good 6 L1 (3)/bis A idem 20 70 Good Good: Exfoliation from the endpart of the photosensitive layer was not observed at all. Medium:Exfoliation from the end part of the photosensitive layer was observedbut a part thereof remained. Bad: Exfoliation from the end part of thephotosensitive layer was severely observed and the whole layer wasremoved.

From the results, in the case where the polycarbonate in which arepeating unit is only composed of the structural formula (3) is used,the electrical properties of the photoreceptors C1 and C2 are good butexfoliation from the end part of the photosensitive layer takes place,so that a problem exists on actual use. Moreover, the photoreceptors D1,D2, E1, and E2 using a resin only composed of bisphenol A or bisphenol Zwhich is well known as a resin for photoreceptors are poor in electricalproperties. Furthermore, even when these resins are mixed, the superiorpoints of both properties cannot be maintained and only the poor pointsare rather emphasized.

On the other hand, it is understood that the photoreceptors A1, A2, B1,and B2 using the copolycarbonate resin according to the invention areexcellent in both of the electrical properties and adhesiveness.

Furthermore, like the polycarbonate resin of bisphenol A, it wasconfirmed that no problem was observed on the solubility towardsolvents.

As is understood from Reference Examples, in the case where adrum-shaped conductive substrate is used, no problem is observed onadhesiveness even when any binder resin is used. Thus, when thehomopolymer of the structural formula (3) is used, photoreceptor drumshaving good electrical properties and showing no problem on adhesivenesscan be obtained even when the resin according to the invention is notused.

Moreover, in the production of the drum-shaped photoreceptors, since thephotosensitive layer is generally formed by dipping, it is not necessaryto peel the photosensitive layer by post-processing and thus easypeeling is not required.

From the above, the use of the copolycarbonate resin according to theinvention exhibits an effect in the case of the sheet-shaped conductivesubstrates and particularly exhibits an effect in the case where aphotosensitive layer-uncoated area is present within the sheet surface.

Example 5

An aluminum-deposited film was provided in a thickness of 70 nm on thesurface of a biaxially oriented polyethylene terephthalate film having awidth of 500 mm and a thickness of 75 μm, surface of which had beenroughened (Ra=0.1 μm) by incorporating silica particles in the film. Theresulting film was wound to form a roll having a length of 2000 m.

Then, aluminum oxide particles having an average primary-particlediameter of 13 nm (Aluminum Oxide C manufactured by Nippon Aerosil Co.,Ltd.) was dispersed in a mixed solvent of methanol/1-propanol byultrasonic wave to thereby form a dispersion slurry of aluminum oxide.This dispersion slurry was mixed with a mixed solvent ofmethanol/1-propanol (weight ratio: 7/3) and with pellets of acopolyamide used in Example 1 with stirring under heating to dissolvethe polyamide pellets. Thereafter, the resultant mixture was subjectedto an ultrasonic dispersion treatment to thereby form a dispersionhaving a solid concentration of 8.0% which contained aluminum oxide/thecopolyamide in a weight ratio of 1/1.

The coating fluid for undercoat-layer formation was applied by reversecoating onto the aluminum-deposited polyethylene terephthalate filmwhile winding off the film from the roll to form an undercoat layer in athickness of 1.2 μm on a dry basis.

Then, 10 parts by weight of oxytitanium phthalocyanine showing strongdiffraction peaks at Bragg angles (2θ±0.2) of 9.3°, 10.6°, 13.2°, 15.1°,15.7°, 16.1°, 20.8°, 23.3°, 26.3°, and 27.1° in X-ray diffractometryusing a CuKα line and 150 parts by weight of4-methoxy-4-methyl-2-pentanone were mixed and subjected to apulverization/dispersion treatment with a sand grinding mill to form apigment-dispersed fluid. Into the pigment-dispersed fluid were mixed 50parts by weight of a 5% by weight 1,2-dimethoxyethane solution ofpoly(vinyl butyral) (trade name Denka Butyral #6000C manufactured byDenki Kagaku Kogyo K.K.) and 50 parts by weight of a 5% by weight1,2-dimethoxyethane solution of a phenoxy resin (trade name PKHHmanufactured by Union Carbide Corporation), and an appropriate amount of1,2-dimethoxyethane was further added thereto to finally prepare adispersion having a solid concentration of 4.0%.

The coating fluid for charge-generating-layer formation thus obtainedwas applied by reverse coating onto the aluminum-deposited polyethyleneterephthalate film on which the undercoat layer had been formed, whilewinding off the film from the roll, to form a charge-generating layer ina thickness of 0.4 μm on a dry basis.

Then, 45 parts by weight of the charge-transporting material composed ofisomers containing a compound of the following structure shown inJP-A-2002-80432, 100 parts by weight of a polycarbonate resin(viscosity-average molecular weight: 22,000) according to the inventioncomposed of the repeating unit (1-1), 8 parts by weight of anantioxidant (trade name Irganox 1076 manufactured by Ciba-Geigy), and0.05 parts by weight of a silicone oil as a leveling agent were mixedinto 640 parts by weight of a mixed solvent of tetrahydrofuran andtoluene (tetrahydrofuran 70% by weight, toluene 30% by weight) toprepare a coating fluid for charge-transporting-layer formation.

The coating fluid for charge-transporting-layer formation thus obtainedwas applied by die coating onto the aluminum-deposited polyethyleneterephthalate film on which the undercoat layer and thecharge-transporting layer had been formed, while winding off the filmfrom the roll, to form a charge-transporting layer in a thickness of 18μm on a dry basis.

The thus obtained roll-shaped sheet on which a photosensitive layer hadbeen applied was cut into a size of 353 mm×584 mm using a continuouscutting machine to obtain a photoreceptor sheet. Furthermore, thephotosensitive layer was peeled from both ends of the sheet in a widthof 25 mm each with acetone and ethanol and the aluminum-deposited layerwas also removed with a sodium hydroxide solution at one end. Thus, anelectrophotographic photoreceptor M was obtained.

The following actual machine test was performed for the photoreceptorsheet M produced.

<Actual Machine Test>

The photoreceptor sheet M was mounted on an on-demand printer,TurboStream manufactured by Hewlett-Packard Co., and image evaluationwas performed. In the mounting, the photoreceptor sheet was wound on thealuminum drum in the machine and the uncoated areas at both ends wereoverlapped to hold the photoreceptor sheet M on the drum. Since thealuminum layer at one end had been removed, they could be easilyoverlapped with electrostatic action.

Using the photoreceptor M, 100 sheets of a half-tone image wascontinuously output but good images were obtained without densitychange. Furthermore, troubles such as exfoliation of the photosensitivelayer from the end part in the machine were not observed and there wasno problem on the actual use.

From the above, it is understood that a photoreceptor excellent in allof electrical properties, image properties, and actual usability(adhesiveness) can be first obtained only in the case where thepolycarbonate resin according to the invention is used.

This application is based on Japanese patent application JP 2010-124832,filed on May 31, 2010, the entire content of which is herebyincorporated by reference, the same as if set forth at length.

1. An electrophotographic photoreceptor comprising a sheet-shapedconductive substrate and a photosensitive layer provided thereon,wherein the electrophotographic photoreceptor contains a photosensitivelayer-uncoated area within the sheet surface, and the photosensitivelayer contains a copolycarbonate resin having a repeating structurerepresented by the following general formula (1):

wherein R¹, R², R³ and R⁴ each independently represent a hydrogen atomor an alkyl group having 4 or less carbon atoms, Z forms a saturatedcyclic aliphatic alkyl group having 5 to 8 carbon atoms including thecarbon atom to be bonded, and the saturated cyclic aliphatic alkyl grouphas one to three methyl groups as substituent(s).
 2. Theelectrophotographic photoreceptor according to claim 1, wherein thecopolycarbonate resin is a copolymer of the repeating structurerepresented by the general formula (1) above and a repeating structurerepresented by the following structural formula (2):


3. The electrophotographic photoreceptor according to claim 2, wherein,in the copolycarbonate resin, the molar ratio of the repeating structurerepresented by the structural formula (2) is larger than the molar ratioof the repeating structure represented by the general formula (1). 4.The electrophotographic photoreceptor according to claim 2, wherein, inthe copolycarbonate resin, the molar ratio of the repeating structurerepresented by the structural formula (2) is twice or more the molarratio of the repeating structure represented by the general formula (1).5. The electrophotographic photoreceptor according to claim 1, whereinthe general formula (1) is represented by the following structuralformula (3):


6. The electrophotographic photoreceptor according to claim 1, whereinthe thickness of the photosensitive layer is 17 μm or larger.
 7. Theelectrophotographic photoreceptor according to claim 1, which containsan insulated part within the sheet surface.
 8. An image-formingapparatus comprising the electrophotographic photoreceptor according toclaim 1.